1. Field of the Invention
The present invention relates generally to electronic apparatuses forming computer systems, and more particularly to a cooling redundancy function suitable for an electronic apparatus in which the same or different multiple units equipped with cooling fans are mounted.
2. Description of the Related Art
As a result of recent developments in computer systems, electronic apparatuses forming computer systems are required to be increased in reliability, and are also required to be reduced in price and size in order to be more competitive on the market. Accordingly, it is necessary to realize highly reliable electronic apparatuses reduced in price and size.
In a conventional electronic apparatus in which the same or different multiple units equipped with cooling are mounted, multiple cooling fans are provided in each unit in order to increase the reliability of the electronic apparatus. For instance, Japanese Laid-Open Patent Application No. 8-124375 discloses such a conventional electronic apparatus in which multiple cooling fans are provided in each unit.
FIG. 1 shows a common electronic apparatus configuration, showing a state before multiple units are mounted in a shelf. FIG. 2 shows a state where multiple units are mounted in the shelf of an electronic apparatus 100 of FIG. 1.
The electronic apparatus 100 of FIG. 1 is, for instance, a computer main body or a magnetic disk unit forming a computer system. An electronic circuit controlling the electronic apparatus 100 is provided in a housing having a front face 102 and a rear face 104, and a shelf part 101 is formed in the electronic apparatus 100. Two shelf part inlets 103 are formed in the front-side end face of the shelf part 101 in the electronic apparatus 100. The shelf part inlets 103 are formed so as to communicate with the outside of the electronic apparatus 100 through the internal mechanism of the electronic apparatus 100.
The shelf part 101 is sectioned into multiple unit mounting parts 105 so as to receive the same or different multiple units equipped with cooling fans. In the case of FIG. 1, the two unit mounting parts 105 are formed to receive two units.
As shown in FIG. 2, two units 10 are mounted in the shelf part 101 of the electronic apparatus 100. As described above, multiple cooling fans are provided in each unit 10 in the conventional electronic apparatus in order to increase reliability. A description is given herein, with reference to FIGS. 3A and 3B, of the configuration of each unit 10.
FIGS. 3A and 3B are perspective views of the configuration of one of the units 10 to be mounted in a conventional electronic apparatus. FIG. 3A shows the front-side appearance of the unit 10, and FIG. 3B shows the rear-side appearance of the unit 10.
The unit 10 shown in FIGS. 3A and 3B is, for instance, a power supply unit to be mounted in a computer main body. The unit 10 includes two cooling fans (not graphically illustrated) to provide a cooling redundancy function. The unit 10 includes an inlet 3 formed in a front face 2, two outlets 5 formed in a rear face 4 opposite the front face 2, and the two cooling fans. The cooling fans draw in cooling air from outside through the inlet 3 and expel the air to and through the outlets 5, thereby cooling a circuit board inside the unit 10.
Next, a description is given of the cooling redundancy function in a case where one of the cooling fans of one of the units 10 shown in FIGS. 3A and 3B fails while the other cooling fans are operating normally in a conventional electronic apparatus including the multiple units 10.
FIG. 4 is a diagram for illustrating the flow of cooling air in the multiple units 10 when the cooling fans are operating normally in the conventional electronic apparatus. FIG. 5 is a diagram for illustrating the flow of cooling air in the multiple units 10 when one of the cooling fans fails in the conventional electronic apparatus.
As shown in FIG. 4, when all the cooling fans are operating normally, in each unit 10, outside air from the corresponding shelf part inlet 103 of the electronic apparatus 100 is drawn in through the inlet 3 (inlet air 3a) and expelled to and through the outlets 5 (outlet air 5a). As a result, cooling air 6a flows through each unit 10 to cool a circuit board therein.
As shown in FIG. 5, when one of the cooling fans fails, in the unit 10 in which the failure occurs, the cooling air 6a hardly flows to the outlet 5 on the side of the failed cooling fan, but the cooling air 6a flows to the outlet 5 on the side of the cooling fan that is operating normally. Accordingly, in the unit 10 in which one of the cooling fans fails, it is possible to ensure a circuit board cooling function to some extent using the other cooling fan. A function for cooling each unit mounted in an electronic apparatus at the time of cooling fan failure as described above is referred to as the cooling redundancy function. However, the flow rate of the cooling air 6a ensured by the cooling redundancy function in the unit 10 in which one of the cooling fans fails is reduced compared with the flow rate of the cooling air 6a when the two cooling fans operate normally.
As described above, in the conventional electronic apparatus, two or more cooling fans including a cooling fan for cooling redundancy are mounted in each unit as a method of providing the cooling redundancy function for multiple units. However, in exchange for an improvement in reliability due to the cooling redundancy function, the mounting of multiple cooling fans in each unit causes an increase in the size of the apparatus as well as an increase in the noise and the price of the apparatus due to an increase in the number of cooling fans.